问题
I have an application which I want to monitor it via perf stat when running inside a kvm VM. After Googling I have found that perf kvm stat can do this. However there is an error by running the command:
sudo perf kvm stat record -p appPID
which results in help representation ...
usage: perf kvm stat record [<options>]
-p, --pid <pid> record events on existing process id
-t, --tid <tid> record events on existing thread id
-r, --realtime <n> collect data with this RT SCHED_FIFO priority
--no-buffering collect data without buffering
-a, --all-cpus system-wide collection from all CPUs
-C, --cpu <cpu> list of cpus to monitor
-c, --count <n> event period to sample
-o, --output <file> output file name
-i, --no-inherit child tasks do not inherit counters
-m, --mmap-pages <pages[,pages]>
number of mmap data pages and AUX area tracing mmap pages
-v, --verbose be more verbose (show counter open errors, etc)
-q, --quiet don't print any message
Does any one know what is the problem?
回答1:
Use kvm with vPMU (virtualization of PMU counters) - https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Virtualization_Tuning_and_Optimization_Guide/sect-Virtualization_Tuning_Optimization_Guide-Monitoring_Tools-vPMU.html "2.2. VIRTUAL PERFORMANCE MONITORING UNIT (VPMU)"). Then run perf record -p $pid and perf stat -p $pid inside the guest.
Host system has no knowledge (tables) of guest processes (they are managed by guest kernel, which can be non Linux, or different version of linux with incompatible table format), so host kernel can't profile some specific guest process. It only can profile whole guest (and there is perf kvm command - https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Virtualization_Tuning_and_Optimization_Guide/chap-Virtualization_Tuning_Optimization_Guide-Monitoring_Tools.html#sect-Virtualization_Tuning_Optimization_Guide-Monitoring_Tools-perf_kvm)
来源：https://stackoverflow.com/questions/35997809/how-can-a-specific-application-be-monitored-by-perf-inside-the-kvm